Series-type voltage regulator

ABSTRACT

A SERIES-TYPE VOLTAGE REGULATOR UTILIZING ON OR MORE PARALLEL REGULATING TRANSISTORS IN WHICH THE UNREGULATED INPUT VOLTAGE IS APPLIED BETWEEN THE EMITTER AND BASE AND THE REGULATED OUTPUT VOLTAGE IS DEVELOPED ACROSS THE COLLECTOR AND BASE, THE OPPOSITE OF THE CONVENTIONAL REGULATOR CIRCUIT. A PARTICULARLY IMPORTANT FEATURE RESIDES IN THE EXTREMELY HIGH RATIO OF REGULATED OUTPUT VOLTAGE TO UNREGULATED INPUT VOLTAGE, FOR EXAMPLE, EVEN IF THE INPUT VOLTAGE DROPS FROM A NOMINAL -20 V. TO APPROXIMATELY -16.5V., A DROP APPROACHING 20%, THE OUTPUT VOLTAGE WILL DROP ONLY VERY SLIGHTLY BELOW THE DESIRED 16 V. OUTPUT VOLTAGE. THIS FEATURE, IN ADDITION TO THE OTHER CIRCUITY OF THE VOLTAGE REGULATOR, PERMITS USE OF THE VOLTAGE REGULATOR UNDER THE EXTREMELY STRINGENT CONDITIONS REQUIRED FOR THE X AND Y DRIVERS OF A COMPUTER CORE MEMORY, WHEREIN ANY NUMBER OF THE CORES ASSOCIATED WITH A PAIR OF X AND Y DRIVE LINES MAY REQUIRED SWITCHING AND WHERE TRANSIENTS AND CURRENT AMPLITUDES MUST BE RIGIDLY CONTROLLED TO PREVENT INADVERTENT CORE SWITCHING.

Feb. 23,1971 I J. H. GRIFFIN 3,566,254

- SERIES-TYPE IVOLTAGE REGULATOR Filed May 19, 1969 JON H. GRIFFIN- BY ERV IN F. JOHNSTON ATTORNEY. JOHN STAN, AGENT.

United States Patent 3,566,254 SERIES-TYPE VOLTAGE REGULATOR Jon Hobart Griflin, Pittsfield, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed May 19, 1969, Ser. No. 825,612 Int. Cl. Gf 1/56 US. Cl. 323-22 5 Claims ABSTRACT OF THE DISCLOSURE A series-type voltage regulator utilizing one or more parallel regulating transistors in which the unregulated input voltage is applied between the emitter and base and the regulated output voltage is developed across the collector and base, the opposite of the conventional regulator circuit. A particularly important feature resides in the extremely high ratio of regulated output voltage to unregulated input voltage; for example, even if the input voltage drops from a nominal v. to approximately 16.5 v., a drop approaching 20%, the output voltage will drop only very slightly below the desired 16 v. output voltage. This feature, in addition to the other circuitry of the voltage regulator, permits use of the voltage regulator under the extremely stringent conditions required for the X and Y drivers of a computer core memory, wherein any number of the cores associated with a pair of X and Y drive lines may require switching and where transients and current amplitudes must be rigidly controlled to prevent inadvertent core switching.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

In the field of series-type voltage regulators, it has been the general practice to employ a regulating tube or regulating transistor wherein the unregulated input voltage is developed in plate or collector circuit and the output voltage is developed in the cathode or emitter circuit. Although such devices have served the purpose of voltage regulation they have not proved entirely satisfactory under all conditions of service, for the reason that considerable difiiculty has been experienced with transient voltages and in obtaining a suflicient amplitude of output voltage for a given input voltage. The input voltage is often standard voltage, such as 12 v. or 28 v., and very often it is desired to obtain a regulated output voltage as close as possible to this input voltage. While there are voltage regulator circuits in the prior art which solve one of the two problems, there are few voltage regulators which solve both problems, and none as well as the subject invention. In addition where special problems are encountered, as in the computer art, few voltage regulators have been completely satisfactory.

In the prior art, one of the prime reasons that considerable difficulty has been experienced in obtaining a regulated output voltage which has a value much more than one-half of the value of the unregulated input voltage, is that, in the conventional series-type voltage regulator there is a resistor connected between the unregulated input voltage source and the base of the regulating transistor, thus providing a base current. The amount of voltage developed across this base resistor controls the amount of current which may be supplied to, or flow in, the base circuit of the regulating transistor. This means that the series regulating transistor cannot operate in a saturated condition, or even close to saturation, because if it did, the voltage developed across the base resistor becomes great enough so that the transistor would start cutting off, or tend to be cut off.

3,566,254 Patented Feb. 23, 1971 In the series-type voltage regulator herein disclosed the base current is supplied through ground, and the regulating transistor can saturate completely, because it takes its base current from ground, that is, the current path is from ground, rather than through a current-limiting base resistor. It is primarily for this reason that there is such a small voltage difference between the unregulated input voltage and the regulated output voltage. Theoretically, the voltage regulator circuit herein disclosed can regulate right down to the saturation drop across the series transistor. The only practical limitation to the amount of current the regulating transistor can handle is the safe maximum current capacity of the transistor.

The specific purpose for which the voltage regulator herein described was designed was to regulate the X and Y drive currents of a special-purpose computer, and to provide transient immunity for a double memory computer subsystem. Since the read and write currents are direct functions of input voltage, any transients will modulate these currents and may cause partial switching of the memory cores. The voltage regulator provides transient immunity by regulating the input voltage.

The following design requirements were taken into account for the regulator, to provide adequate regulation and transientimmunity for the drive currents of the double memory subsystem.

(1) The regulator shall be capable of being adjusted to a nominal output voltage of 16.0 v. D-C i0.1% at a nominal output current of 120 ma. :1% and a nominal input voltage of 20.2 v. i1%.

(2) The regulator shall regulate to within 0.5% for any instantaneous or steady state change of output current from 0 to 200 ma.

(3) The regulator shall regulate to within 0.5% for any instantaneous or steady state change of input voltage from 18 v. D-C to 22 v. D-C.

(4) The regulator shall be capable of providing a 100 to 1 reduction of input ripple voltage.

(5) The regulator shall operate properly within an ambient temperature range from 0 C. to +45 C. with an output voltage drift rate of less than :3 mv./ C. when adjusted at an ambient temperature of +25 C.

(6)The regulator shall be able to withstand a 4.0 v. positive going transient of 5 msec. duration and the change at the output shall be no greater than 1.0 volt.

(7) The initial charging current for the output capacitors shall be less than 360 ma.

(8) The output voltage of the regulator shall be zero volts until commanded by an external relay closure to provide its nominal output voltage of -l6 v.

Discussing now the objects of the inventions, one object of the present invention is the provision of a voltage regulator wherein the regulated output voltage is an appreciable fraction of the unregulated input voltage, as much as or more of the input voltage.

Another object is to provide a voltage regulator wherein the current capacity of the regulating transistor is not limited by the amount of base current that the regulating transistor can handle.

A further object of the invention is the provision of a voltage regulator having an extremely simple circuit.

Still another object of the invention is to provide a regulator capable of providing a to 1 reduction of input ripple voltage.

Yet another object of the present invention is the provision of a regulator which is capable of regulating to within 0.5% for any instantaneous or steady state change of output current from 0 to 200 ma. or for any instantaneous or steady state change of input voltage from 18 v. D-C to 22 v. D-C.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIG. 1 is a schematic drawing of a simplified basic form of the series-type voltage regulator.

FIG. 2 shows a complete circuit diagram of the seriestype voltage regulator of this invention, using only one regulating tube.

FIG. 3 is a complete circuit diagram of the series-type voltage regulator, utilizing two regulating tubes and adapted for use with the X and Y core drivers of a memory subsystem of a computer.

Referring now to the drawings, wherein like reference numerals designate like or corresponding parts throu hout the several views, there is shown in FIG. 1 a simplified embodiment of a series-type voltage regulator connected to input terminals 12 and output terminals 14. The emitter of the regulating transistor Q1 is adapted to be connected to an unregulated input voltage source V and, at the collector, a regulated output voltage V may be obtained.

A driving transistor Q3 has its collector connected to the base of the regulating transistor Q1 and its emitter adapted for connection to the unregulated input voltage source V at one of the input terminals 12. Generally, a resistor Rbl is inserted between the base of Q1 and the collector of Q3 to limit the amount to the collector of Q3.

A voltage-reference device is connected to the emitter of the driving transistor Q3. In FIG. 1 the voltage reference device is a Zener diode CR1. However, the voltagereference device could be a gas-type voltage-reference tube employing a glow discharge. The resistor R7 has the function of reducing the input voltage V to the proper value at the input of the voltage reference device CR1.

In a specific embodiment actually built, regulating transistor Q1 was an n-p-n type transistor for voltage regulation of a negative input voltage V In this instance, driving transistor Q3 was a p-n-p type transistor.

For regulating a positive input voltage V regulating transistor Q1 would be a p-n-p type transistor and driving transistor Q3 would be a n-p-n type transistor.

The terminal 16 connected to the base of the driving transistor Q3 is connected to some point in the regulator circuit 10 wherein the voltage varies With the variation in regulated output voltage V The regulator herein described was designed to provide anegative 16 v. regulated output voltage V from a nominal negative 20 v. input voltage V and maintain this output voltage within specified limits under varying input and load conditions, as described hereinabove.

FIG. 2 is a schematic representation of the complete voltage regulator 20, When power is applied at input terminals 12, resistor R10 and Zener diode CR2 assure that transistor Q3 will conduct to drive the series regulator transistor Q1, which supplies current to the load, through output leads 14.

The sensing resistors R14, R15 and R16 compare a portion of the output voltage V with the reference voltage, established by VBE(Q4 and CR3, where VBmQr) is the voltage drop across the base-to-emitter of transistor Q4. Any error in output voltage is amplified by Q4 through Q1, and is fed back to the output out of phase with the original error voltage, thereby controlling the output voltage.

Consider the situation when the output voltage V attempts to increase. The change in voltage is reflected through the divider action of R14, R15 and R16 to the base of transistor Q4, resulting as a change in base current. This change in base current is amplified by transistor Q4 as an increase in collector current. Since the current through resistor R11 must remain constant due to the voltages established by Zener diodes CR2 and CR1 and the base-emitter drop of transistor Q3, an increase in the collector current of transistor Q4forces a decrease in Q3 base current; and hence, a corresponding decrease in Q3 collector current. This reduces the base drive for the series regulator transistor Q1 and forces the output voltage V to return to its nominal value. The value of the output voltage V is adjustable to some extent by the potentiometer R15.

Reference is now directed to FIG. 3, which shows the complete voltage regulator 30, designed for specific use with the memory of a computer subsystem. In order to not destroy the contents of the memory when the computer is first turned on, the complete voltage regulator 30 must not produce an output voltage until the control logic has been cleared. The output is maintained at zero volts by breaking the base drive source to transistors Q1 and Q2, with the relay bar 32C in the position shown in FIG. 3. After a certain predetermined interval, when the control logic is cleared, the relay bar 32C grounds the input circuit through contacts 32B and ground,

The function of this relay 32 was to insure that the output voltages V OUT and V OUT did not build up before the memory control logic had been cleared. With the relay 32 in the grounded position, the voltage regulator 30 works as a normal regulator. With relay 32 open, the output voltage equals 0. With relay grounded, the voltage regulator 30 puts out its required voltage. Pull output voltage is obtained after the charging capacitor C becomes fully charged. Base current is now available to transistors Q1 and Q2 and the output voltage will gradually rise to the nominal 16- v. (negative) output.

For computer use, in order to establish the proper drive currents for the cores, the current-determining resistance in the core drivers circuit required for the original 20 v. source must be reduced to compensate for the new 16 v. source at V OUT and V This is accomplished by paralleling the current-determining resistors in the X drivers by R17 and in the Y drivers by R18. The resistance values chosen provide 170 ma. of half-select currents.

It will be noted that, While in FIG. 3 regulating transistors Q1 or Q2 are in parallel, the voltage regulator is actually a series-type, with the transistors being in parallel solely to double the amount of output current and hence the output power. The total peak load current to be supplied by the regulating transistors is 200* ma. The maximum duty cycle is 4 ,usec. out of a 6.4 ,usec. period. Two G306 transistors Q1 and Q2 were used in parallel for power dissipation purposes and to minimize the saturation voltage across the series regulating element. The power in each series regulator transistor is:

Base resistors R4 and R5 and emitter resistors R22 and Rel were used with each of the series regulating transistors Q1 and Q2, respectively, to provide current sharing. Each collector must supply ma. peak current under full load conditions.

Of course, more than two regulating transistors may be placed in parallel if more output current is desired, with each transistor having a current-equalizing resistor in its emitter and base circuits.

The nominal base current of transistor Q4 is where I =the collector current through transistor Q4 and j34=the B of transistor Q4. The nominal current through the sensing voltage divider consisting of R14, R15 and R16 should be approximately 100 times the base current of transistor Q4, or 5.0 ma. for good stability.

Solving for the total resistance of the sensing divider yields:

16 v. RTOT- ma.

The G313 Zener diode was chosen as the reference diode because its temperature coefiicient when biased just under 5 milliamps tracks temperature variations of V The resistor R6 (3.9K) plus the emitter current of transistor Q4 provides the current needed to bias Zener diode CR3 properly. The value of the reference diode CR3 sets the required values of Zener diodes CR1 and CR2 for proper operation. The resistors R7 (2.2K) and R10 (47012), respectively, were used to assure ample bias currents for these diodes.

The resistors actually used in the model built were RM- series film resistors, which are generally 1% tolerance resistors, especially the power resistors. All resistors need not have this close a tolerance about the values shown, however, this ensured operation within the operating parameters indefinitely, even with changes with time of resistor values.

The function of the output capacitor C is to supply current to the load during the time that the voltage regulator 30 is disabled because of an input transient of sufficient magnitude to saturate transistors Q1 and Q2. The capacitor used was a 450 ,llfd. unit.

Optimum half-select drive currents were empirically determined to be 170 ma. This fixed the values of the output shunt resistors R17 and R18 to be 3659 each.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a series-type voltage regulator, including input terminals and output terminals, one input terminal and one output terminal being grounded, the other input terminal adaptable for connection to an unregulated voltage source and the other output terminal adaptable for connection to an output load across which appears the regulated voltage, the combination comprising:

a regulating transistor comprising:

an emitter connected to the ungrounded input terminal; a collector connected to the ungrounded output terminal; a base connected to a resistor; a driving transistor, comprising:

a collector connected to the base of the regulating 7 transistor through the first-named resistor;

an emitter connected tothe ungrounded input terminal through a second resistor;

a base;

a first voltage-reference device, in the form of a first Zener diode, connected between the emitter of the driving transistor and ground;

a voltage-sensing circuit, connected across the output terminals of the voltage regulator, having at least one point at which the voltage varies in accordance with the variation in output voltage;

the voltage-sensing circuit comprising a resistor, po-

tentiometer and another resistor all in series with each other; and wherein the base of the driving transistor is operatively connected to the center tap of the potentiometer, this being the point at which the voltage varies;

a sensing amplifier whose input is connected to the point which senses the variation in the output voltage and whose output is connected to the base of the driving transistor;

the sensing amplifier comprising a p-n-p transistor whose base is connected to the center tap of the potentiometer and whose collector is connected to the base of the driving transistor;

the sensing amplifier having associated with it the following circuitry:

two resistors connected in series between the ungrounded input terminal and the collector of the sensing amplifier;

a second Zener diode connected between the junction of these two last-named resistors and the grounded terminal;

a resistor connected between the collector of the regulating transistor and the emitter of the sensing amplifier; I

a third Zener diode connected between the emitter of the sensing amplifier and the grounded terminal; and

an output capacitor connected across the output terminals.

2. A voltage regulator according to claim 1 wherein:

the regulating transistor is an n-p-n transistor and the driving transistor is a p-n-p transistor.

3. A voltage regulator according to claim 1, wherein:

the regulating transistor is a p-n-p transistor and the driving transistor is an n-p-n transistor.

4. A voltage regulator according to claim 1, further comprising:

an output resistor between the ungrounded side of the output capacitor and the ungrounded output terminal.

5. A voltage regulator according 0 claim 4, further comprising:

another output resistor;

another ungrounded terminal, the other output resistor being connected to this terminal and the ungrounded side of the output capacitor, and

a relay capable of interrupting the path between the junction of the first Zener diode and ground, thereby inhibiting a regulated output voltage for a predetermined interval.

References Cited UNITED STATES PATENTS 2,976,474 3/1961 Dodge 32322XT 3,079,543 2/1963 Decker 32322T 3,319,150 5/1967 Elich et al 32322XT 3,344,340 9/1967 Webb 323-22T J D MILLER, Primary Examiner A. D. PELLINEN, Assistant Examiner U.S. Cl. X.R. 32338 

